Due to the limited summer work period in Arctic regions, it frequently is desirable to lay offshore pipelines during the wintertime. This usually necessitates cutting ice slots so that the pipeline may be laid through the ice slot and down to the sea bottom. When underwater pipelaying is undertaken through an opening in the ice, it is often necessary to support large loads from the surface by means of cranes, "A"-frames, etc. Such loads are usually supported directly from the ice. However, as the weight of the load is increased it becomes necessary to distribute the load support over a very wide area on the ice away from the edge of the ice slot. If this is not done, excessive deflections or stresses in the ice may result, possibly leading to failure and injury to personnel or damage to equipment. One means by which loads may be distributed is by the use of so-called straddle cranes, or by large trusses to carry the point of load application well away from the opening in the ice. As the suspended load becomes very large, so does the supporting structure; in fact, the weight of the structure may approach or even exceed the weight of the pipeline.
To some degree, the load capacity of the ice may be increased by artificially thickening the ice by controlled flooding and freezing as is done in construction of ice roads. This is time consuming and costly and may be undesirable in pipeline construction because of the added volume of ice that must then be cut and removed.